Corona triode voltage regulator



April 10, 1951 c. M. TURNER CORONA TRIODE VOLTAGE REGULATOR Filed Sept. 1, 1950 6' UPPL Y AMPL /F/E/? ERROR \S/G/VAL INVENTOR. CLAQE/VCE M ERNIE-7? Patented Apr. 10, 1951 CORONA TRIODE VOLTAGE REGULATOR Clarence M. Turner, Stony Brook, N. Y., assignor to the United States of America as represented by the United States Atomic Energy Commission Application September 1, 1950, Serial No. 182,849

8 Claims.

The presentinvention relates to an improved method and means of regulation employing corona discharge and is more particularly concerned with voltage regulation of the high voltage shell of. a Van de Graafl electrostatic generator by means of electronically controlled corona discharge.

At the outset, it is to be noted that the term corona discharge as herein employed is taken to denote electrical discharge produced by a voltage which is greater than the ignition voltage and less than the breakdown voltage. General considerations relating to plane electrodes indicate that corona discharge only esults when the prodnot of the pressure of the gas between the electrodes and the distance between the electrodes is less than the critical value for minimum ignition potential as determined by Paschens Law; however, where needle electrodes are employed ignition is followed by an increase in the effective length of the discharge rather than a decrease as occurs with plane electrodes, and thus the phenomena of corona discharge is observable regardless of the pressure and spacing of the electrodes. In a corona discharge the voltage required to produce a particular current is directly proportional thereto and within a definite range there is no danger of breakdown. These characteristics of corona discharge make it admirably suited for regulatory purposes and it is so employed in the present invention.

Although the applications of the present invention are manifold, the invention is particularly advantageous in the regulation of the potential of the high voltage electrode of a Van de Graaff electrostatic generator and therefore the following disclosure is referenced thereto. As Van de Graafi generators in general are well known in the art, no detailed discussion thereof is presented; however, reference is made to my copending application Serial No. 750,465, filed May 26, 1947, for a complete disclosure of an improved apparatus of this type with which the present invention may be advantageously associated. It should be noted with regard to Van de Graaff generators that one of the more difficult problems associated therewith is the precise regulation of the potential of the high voltage electrode or shell because of the extremely high voltages involved and the relative inaccessibility of the high voltage electrode. In the past, mechanical motion of regulating means within the shell has been employed; however, the disadvantages of such a system are numerous and the present inventionis adapted to obviate these disadvan- 2 tages as well as the above-noted difficulties in a manner set forth below.

It is an object of the present invention to provide improved method and means for voltage regulation.

It is an object of the present invention to provide improved method and means for controlling a corona discharge.

It is an object of the present invention to provide improved corona discharge means for voltage regulation.

It is another object of the invention to provide an improved method and means for electronically controlling the voltage of an electrode.

It is still another object of the present invention to provide improved method and means of electronically controlling a corona discharge voltage regulator.

It is a further object of the present invention to provide improved grid control for a corona discharge voltage regulator.

It is a still further object of the present invention to provide an improved method and means of regulating the potential of electrodes of a Van de Graaff electrostatic generator without recourse to moving parts.

Numerous other objects and advantages of the invention will be apparent from the following disclosure which may be best understood when considered together with the accompanying drawing which is a schematic illustration of the invention with associated electrical equipment. For convenience of description the invention is shown in combination with the shells of a Van de Graaff electrostatic generator, as for example, the generator disclosed in my copending application noted above, wherein means such as fixed corona gaps operate to maintain fixed potential differences between the individual shells of the generator.

Considering now the invention as shown in the drawing it will first be noted that a plurality of corona needles I are directed toward an electrode whose potential is to be regulated, as in this instance high voltage shell 2, shown only in fragmentary View. Needles l are disposed in generally perpendicular relationship to shell 2 at a distance therefrom and are interconnected through individual resistors 3 which operate to stabilize the corona discharge from needles Between needles I and shell 2 there is provided a screen or grid electrode 4 which is preferably adjacent needles I.

The electrical elements of the invention include a power supply 6 and a variable impedancasuchas for example vacuum tube I connected in series between grid 4 and needles I. In the illustrated embodiment of the invention the positive terminal of power supply '6 is connected to grid 4 and the negative terminal is connected. to the cathode 8 of tube I which in turn has its anode 9 connected through resistors 3 to needles I. The negative terminal of power supply 6 may also be grounded if the polarity of the corona discharge is proper to make such connection feasible.

From the above description it is apparent that power supply 6 provides the requisite potential between needles I and grid 4 to produce corona discharge therebetween and further that the amplitude of this potential and thus the magnitude of the corona discharge may be varied by controlling the impedance of tube I. Tube I is provided with a control electrode II by means of which the desired impedance variation is accomplished. An error signal, supplied from the regulating phenomenon, is applied to control electrode II which thereby causes the impedance of tube 1 to vary accordingly, which consequently provides the requisite corona discharge control, as noted above. An amplifier I2 may be provided to intensify the error signal to the point where proper control of tube I is obtained if, as is usually the case, the error signal is relatively weak and thereby unsuited for direct use as a regulating signal.

As noted above, needles I are directed toward the electrode whose potential is to be regulated, such as high voltage shell 2 of a Van de Graaif electrostatic generator. In such an application grid 4 may be advantageously inserted in an aperture I3 formed in the tank wall I4 of the generator and aligned with the wall in order to reduce distortion of the electrostatic fields within the generator. The components hereinbefore described and comprising the corona discharge regulator may be enclosed in a secondary envelope, not shown, which is secured about aperture I3 in tank wall I4 in a gas-tight manner, or alternatively, only the corona needles need be so enclosed and the associated electrical apparatus may be situated at a distance therefrom with electrical connections from needles I and grid 4 emerging from the secondary envelope through gas-tight seals. In the present application of the invention the high voltage electrode or shell 2 may be maintained at a positive potential and tank wall l4 may be grounded, in which case the above noted polarity of power supply 6 and grounding connections thereof, would be proper.

Considering the operation of the invention with reference to the regulation of the voltage of high voltage shell 2 of a Van de Graaif electrostatic generator and assuming energization not only of the electrostatic generator but also of the requisite portions of the invention, it will be noted that a corona discharge is established between needles I and grid 4 by virtue of the potential impressed therebetween by power supply 6. This potential is chosen so that under operating conditions a corona discharge is established rather than ignition which would occur if the potential employed were too large. an open construction, such as for example wire mesh, and thus is pervious to the corona discharge from needles I. Shell 2 is maintained at a high positive potential by electrical apparatus integral with the Van de Graaff generator and, as grid 4 is maintained at a much less posi- Grid 4 has.

tive potential, a certain amount of the corona discharge between needles I and grid 4 will be attracted through grid 4 and on to shell 2 where it impinges. The current flow to shell 2 is controlled to vary or regulate the potential of shell 2. It is thus to be noted that the value of the potential of grid 4 is chosen so that corona discharge will occur between needles I and grid 4 and that a small fraction of the discharge will pass through grid 4 and impinge upon shell 2. Under these conditions the magnitude of the corona discharge is substantially independent of the value of the potential of shell 2.

Regulation is accomplished by applying a signal to the control electrode II of vacuum tube 1 which, for convenience, is herein designated as an error signal as further explained below, and which thereby varies the impedance of tube I. As tube I is connected in series with power supply 6 between needles I and grid 4 a variation of the impedance thereof produces a related variation of the value of the potential impressed between needles I and grid 4 which thereby influences the magnitude of the corona discharge. Variation of the corona discharge produces a.,corresponding variation in the discharge current reaching shell 2 and thus varies the potential thereof.

The error signal impressed upon control electrode II of tube 7 to vary the impedance of tube I may be obtained from a variety of sources, the choice of which is dependent upon the particular phenomenon which it is desired to main-- tain constant. For example, the error signal may be provided by the voltmeter conventionally attached to shell 2 or may be derived from the ion beam emerging from the Van de Graaff generator and, as noted above, may be amplified by a conventional amplifier circuit I2 if too weak to provide an adequate signal for control of vacuum tube I. high voltage electrode 2 may be readily regulated even though an intermediate shell be employed between shell 2 and tank wall I4, as there is conventionally provided means for maintaining a fixed potential difference between high voltage electrode 2 and an intermediate shell, reference in this respect being made to my copending application cited above. Regulation of the potential of an intermediate shell would thus operate to regulate the potential of the high potential electrode and produce the same result as if no intermediate shell were present.

From the foregoing it is apparent that corona discharge regulation of the potential of a high potential electrode is accomplished by the present invention without the inclusion of moving parts or the necessity of mechanical motions, such as movement of the corona needles as has heretofore been the practice. The corona discharge is originally established by the choice of appropriate potentials and spacing and is thereafter controlled by varying the potential producing same, which variation is controlled and employed to accomplish regulation, as for example of the potential of the high voltage shell of a Van de Graaff electrostatic generator.

It will be appreciated that the invention is equally applicable in connection with the regulation of a negatively charged electrode; however, in such an application it has been found advantageous to reverse the electrical connections of vacuum tube I and power supply 6.

whereby plate 9 of tube I is connected to grid 4 and the positive terminal of power supply 6 is Furthermore, the potential of- 5 connected to needles I. It has also been found advantageous in certain instances to provide a complete shielding of needles I by grid 4 to prevent sparking to shell 2; however, as such techniques are well known no detailed description thereof is necessary.

While the present invention has been described with reference to but a sole preferred embodiment and one particularly advantageous application thereof, it will be apparent to those skilled in the art that numerous modifications and variations of the invention are possible within the spirit and scope thereof and that innumerable applications are possible, and thus no limitation is intended by the terminology or mode of description employed but instead reference is made to the following claims for a precise definition of the novelty of the invention.

What is claimed is:

1. A corona discharge voltage regulator comprising an electrode whose voltage is to be regulated, a plurality of corona discharge needles directed toward said electrode at a predetermined distance therefrom, a grid electrode disposed adjacent said needles intermediate said needles and said electrode, power supply means impressing a potential difference between said grid and said needles whereby corona discharge is produced therebetween, said grid being maintained at a potential intermediate said needles and said electrode whereby a predeterminable fraction of said corona discharge extends from said needles to said electrode through said grid, and means to vary the potential difference between said grid and said needles in accordance with the potential of said electrode whereby the magnitude of said ,corona discharge and the fraction thereof reaching said electrode is varied to control the potential of said electrode.

2. A corona discharge voltage regulator for a high voltage electrode comprising a plurality of corona discharge needles directed toward said electrode at a distance therefrom, an apertured grid structure disposed intermediate said needles and said electrode, power supply means impressing a potential difference between said needles and said grid whereby a corona discharge is established therebetween, means maintaining said grid at a potential intermediate said needles and said electrode whereby a predeterminable fraction of said corona discharge between said needles and said grid reaches said electrode and influences the potential thereof, voltage control means connected between said needles and said grid to control the voltage therebetween, and er ror signal producing means responsive to the potential of said electrode and connected to said voltage control means to vary the control thereof whereby the magnitude of the corona discharge and consequently the potential of the high voltage electrode is controlled thereby.

3. A corona discharge voltage regulator for the control of the potential of a high voltage electrode comprising a perforated grid structure disposed adjacent said high voltage electrode, a plurality of corona discharge needles directed toward said high voltage electrode and separated therefrom by said grid, said needles and said grid being separated and maintained at different potentials with said grid being at a potential intermediate said needles and said electrode whereby corona discharge occurs between said needles and said grid and a known fraction thereof reaches said electrode, and means tovary the potential difference between said needles and said grid whereby the magnitude of the corona discharge therebetween is controlled to vary the discharge reaching said high voltage electrode.

4. A corona discharge device for controlling the potential of an electrode having a high potential impressed thereon, and comprising a corona discharge needle directed toward said electrode and spaced therefrom, said needle being at a different potential than said electrode, an apertured grid disposed intermediate said needle and said electrode and maintained at a potential intermediate said needle and electrode, power supply means connected between said needle and said grid whereby corona discharge is established therebetween and in part reaches said electrode, and means to vary the potential difference between said grid and said needle in accordance with the potential of said electrode to control the magnitude of the corona discharge between said needle and said grid, thereby controlling the amount of discharge reaching said electrode and consequently controlling the potential thereof.

5. A corona discharge voltage regulator for controlling the potential of an electrode having a positive potential thereon and comprising corona discharge means including an apertured grid and a plurality of needles substantially directed toward said apertured grid structure and having a potential difference impressed therebetween whereby corona discharge is therein established, said corona discharge means being disposed with the grid thereof adjacent said electrode whereby a known fraction of said corona discharge impinges upon said electrode thereby determining the potential thereof, vacuum tube means having a control member and being connected between said needles and said grid for varying the potential therebetween in accordance with the potential of said control member, and means responsive to the potential of said electrode for impressing a potential upon said control member in accordance with the potential of said electrode whereby the magnitude of said corona discharge and the fraction thereof impinging upon said electrode is varied to control the potential of said electrode.

6. A corona discharge device for regulating the potential of an electrode at a high positive potential and comprising a plurality of needles generally directed toward said electrode at a distance therefrom and maintained at a negative potential with respect thereto, an apertured grid structure intermediate in spacing and potential to said needles and said electrode, power supply means connected between said needles and said grid for increasing the potential difference therebetween whereby corona discharge is established from said needles to said grid, a fraction of said corona discharge passing through said grid to said electrode by virtue of the positive potential of said electrode and thereby influencing the potential of said electrode, variable impedance means connected in series with said power supply means between said needles and said grid for varying the potential impressed therebetween and having control means indirectly connected to said electrode for varying said variable impedance in accordance with the potential of said electrode, whereby the magnitude of said corona discharge and the portion thereof impinging upon said electrode is varied to maintain a desired potential upon said electrode.

'7. In combination with the high voltage electrode of a Van de Graaff electrostatic generator, a corona discharge device comprising a plurality of needles directed toward said electrode at a distance therefrom whereby a potential difierence exists therebetween, an apertured grid disposed intermediate said needles and said electrode, power supply means impressing a potential between said needles and said grid to establish a corona discharge therebetween, a portion of said discharge passing through said grid and impinging upon said high voltage electrode, and electronic means controlling said power supply means to vary the corona discharge in accordance with the potential of said high voltage electrode thereby regulating the potential of said high voltage electrode.

8. In combination with the high voltage electrode of a Van de Graaff electrostatic generator having a tank envelope, a corona discharge voltage regulator comprising an apertured grid disposed Within an aperture in said tank in insulated relation to said tank, a plurality of needles 8 directed toward said high voltage electrode on the opposite side of said grid therefrom and adjacent said grid, potential supply means connected between said needles and said grid and impressing a potential therebetween with said grid being at a potential intermediate said needles and said high voltage electrode, said potential difference establishing a corona discharge between said needles and said grid whereby a fraction of said discharge passes through said grid to said high voltage electrode, variable impedance means connected between said needles and said grid and having control means, said control means being responsive to the potential of said high voltage electrode whereby the magnitude of said corona discharge is controlled and the potential of said high voltage electrode regulated.

CLARENCE M. TURNER.

No references cited. 

